At present, a platinum catalyst is used in many chemical reactions and next-generation batteries. However, there are many problems to be solved, such as limited platinum reserves, an increase in cost due to use of platinum in a polymer electrolyte fuel cell (PEFC), and occurrence of a chemical reaction such as decomposition of an electrolyte solution by platinum, as well as an increase in cost due to use of platinum in an air cell. Therefore, an alternative technology which does not use platinum has been developed.
That is, hitherto, for example, Patent Literature 1 proposes a fuel cell using, as an electrode catalyst, a metal oxide such as ruthenium oxide, titanium oxide, vanadium oxide, manganese oxide, cobalt oxide, nickel oxide, or tungsten oxide or a metal nitride such as molybdenum nitride.
In addition, Patent Literature 2 proposes a carbon catalyst for a fuel cell, which is obtained by: adding a metal compound containing at least one of iron, cobalt, nickel, chromium, and manganese to a raw material for producing non-graphitizable carbon; mixing the components; and performing a carbonization treatment by firing, and has a carbon nano-onion structure laminated and developed in an onion form around metal particles. Further, Patent Literature 3 proposes a carbon catalyst for a fuel cell, which has a nanosized shell-like structure as disclosed in Patent Literature 2 and is doped with nitrogen by a liquid-phase doping method or a gas-phase doping method.